package collection;

import java.util.Collection;

public class CollectionDemo1 {
    public static void main(String[] args) {
        //Collection c = new java.util.ArrayList();
        Collection c = new java.util.HashSet();
        c.add("one");
        c.add("two");
        c.add("three");
        c.add("four");
        c.add("five");
        boolean b = c.add("one");
        //c.clear();//清空集合
        System.out.println(b);
        System.out.println(c);
        System.out.println(c.size());
        System.out.println("是否是空集:"+c.isEmpty());
    }
}